Current potential indicator

ABSTRACT

A current potential indicator for connection with electrical contacts for detecting with a minimum event indicator the presence of a minimum electrical energy potential available at the contacts, and a threshold indicator for sensing a selected quantity of electrical energy above said minimum energy level. The apparatus is specially adapted for insertion into a pyrotechnic cartridge well or breech cap of a weapons system using pyrotechnically discharge weapons by utilizing a housing with retainer means for releasable connection with the well or breech cap. No electrical power supply is required for operation of this current potential indicator, thus producing essentially fail safe reliability.

Williams et al.

[ June 25, 1974 CURRENT POTENTIAL INDICATOR [75] Inventors: Robert A.Williams; David M. Holt,

both of Fort Worth, Tex.

[73] Assignee: Williams Instruments, Inc., Fort Worth, Tex. by saidWilliams [22] Filed: Oct. 30, 1970 [21] Appl. No.: 85,693

[52] US. Cl 324/133, 324/72.5, 324/103 R [51] Int.Cl G011 19/14, G0lr19/16 [58] Field of Search 324/103, 103 P, 133, 72.5,

324/158 P, 158 R, 73 R; 339/177 [56] References Cited UNITED STATESPATENTS 2,877,419 3/1959 East 324/149 2,926,245 2/1960 Denk 325/3963,024,388 3/1962 Blitchington, Jr 324/73 R 3,046,482 7/1962 East 324/1333,315,246 4/1967 Huffman 324/133 3,412,392 11/1968 Jenkins 324/1333,437,916 4/1969 Mazurkeuics 1. 324/133 3,505,635 4/1970 Williams339/177 3,667,037 5/1972 Kierce 324/73 R OTHER PUBLICATIONS Sturley, K.R., Radio Receiver Design, part 11, John Wiley & Sons, 1948, page 133.

Primary ExaminerAlfred E. Smith Assistant ExaminerE. F. Karlsen llttorney, Agent, or F irm- Arthur F. Zobal; Wofford, Felsman, Fails &Zobal [57] ABSTRACT A current potential indicator for connection withelectrical contacts for detecting with a minimum event indicator thepresence of a minimum electrical energy potential available at thecontacts, and a threshold indicator for sensing a selected quantity ofelectrical energy above said minimum energy level. The apparatus isspecially adapted for insertion into a pyrotechnic cartridge well orbreech cap of a weapons system using pyrotechnically discharge weaponsby utilizing a housing with retainer means for releasable connectionwith the well or breech cap. No electrical power supply is required foroperation of this current potential indicator, thus producingessentially fail safe reliabillty.

10 Claims, 3 Drawing Figures CURRENT POTENTIAL INDICATOR BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates ingeneral to electrical test apparatus, and in particular to apparatus fortesting the energy level across the electrical contacts in an electricaldetonator circuit used to fire a pyrotechnic cartridge in a weaponssystem such as those used on military aircraft.

2. Description of the Prior Art Previously, apparatus and systems havebeen developed for testing detonator circuits in weapons systems todetect spurious electrical energy when the detonator circuit isintentionally energized, or a selected threshold quantity of electricalenergy when the system is deenergized.

As explained in U.S. Pat. No. 3,505,635, pyrotechnic cartridges are nowextensively utilized in aircraft for ejecting bombs or other weapons.These cartridges are releasably connected with electrical circuitry,which when energized, detonates the cartridge, thus emitting ahigh-pressure gas which may, for example, release a latching device andimmediately thereafter eject a bomb. Such devices have proven dangerousduring the arming of aircraft previous to missions. Premature ejectionof a bomb occurs upon inserting one of the cartridges into a well inwhich the detonator circuit has been accidentally or inadvertentlyenergized. Accordingly, it is essential that the detonator circuit ofsuch devices be tested prior to arming the weapons system for thepresence or level of electrical energy.

A satisfactory test probe for insertion into a pyrotechnic cartridgewell or breech cap is disclosed in U.S. Pat. No. 3,505,635. In suchdevices, the test indicators which detect the quantity of electricalenergy across the electrical contacts in a pyrotechnic cartridge well orbreech cap are located on the exterior of the test probe, usually in aconsole electrically connected with the test probe. Commonly, suchconsole contains electrical circuits and power sources, which themselvesare capable of malfunction, with the result that it is sometimesdifficult to know with certainty whether the pyrotechnic detonatorcircuit or the test circuit is defective.

It is accordingly, the general object of this invention to provide asmall, protable and rugged test instrument requiring no batteries orsupplemental power supply for testing various aircraft weapons releasefiring signals with essentially fail-safe reliability.

Another object of the invention is to provide a current potentialindicator, especially suitable for weapons systems testing, that utilizea test probe, an electrical minimum event indicator to detect a minimumamount of electrical energy, and an electrical threshold indicator forsensing a selected quantity of electrical energy above said minimum.

Another object of the invention is to provide in a weapons test system acurrent potential indicator including a minimum event indicator and athreshold indicator combined with a constant current source for greateraccuracy in sensing selected quantities of electrical energy, suchapparatus being self-contained, without need for attachment to aseparate test console.

Another object of the invention is to provide a current potentialindicator for use in weapons systems including a minimum event indicatorand a threhold indicator, as well as reisitance means that is variableto enable selection of the quantity of energy that activates thethreshold indicator.

Another object of the invention is to provide a current potentialindicator, especially suitable for weapons systems testing, includingload disconnect means for disconnecting the circuit after a selectedinterval of electrical energy application.

SUMJVIARY OF THE INVENTION Broadly, the invention consists of a testprobe having a pair of electrical contacts adapted to engage matingcontacts in a weapons systems cartridge well or breech cap, a minimumevent indicator to sense a selected minimum quantity of electricalenergy, a threshold indicator to sense a selected quantity of electricalenergy above said minimum, and a circuit means connecting the contactswith the minimum event and threshold indicators for actuation thereof.

Describing briefly circuit means for accomplishing the above atransistor Q1 (see FIG. 2) acts as a constant current source for aprogrammable unijunction transistor (PUT) Q2, transistor Q3, and an RCnetwork comprising R5 and Cl. If the voltage input to the probeincreases, the potential across resistor R4 also increases until it issufficient to turn te transistor Q3 on. When Q3 turns on, its collectorpulls to ground, turning transistors Q4 and Q7 on. When Q7 turns on itsupplies current to indicator K2, which is a minimum event indicator.When Q4 turns on,'it supplies base current to the power transistor Q5,turning it on. Transistor 05 must only be capable of carryingapproximately four amperes, since transistor Q4 is connected to currentlimit at approximately 1 50 milliamperes of base current for transistorQ5, which will limit the maximum collector current drawn through Q5.

The threshold circuit comprises a transistor 06, resistors R14, R15, R16and an indicator K1. This circuit is connected directly across a loadresistor R13 to detect the threshold currents through the load, and maybe adjusted from approximately two to four amperes as a selectedthreshold range. Whenever the voltage across R13 is sufficient,transistor Q6 turns on, supplying current to indicator Kl to cause it toswitch.

Since the firing pulse may be applied to the circuit for any length oftime, depending upon how long the operator depresses the weapon systemfire button, provision has been made to disconnect the load from thefiring circuit after approximately 15 milliseconds. When the minimumcurrent transistor Q1 turns on, the voltage across resistor R4 isapplied to transistor Q2 and the R5 and Cl network. Capacitor Cl isnormally discharged,

. but when the transistor Q1 turns on the capacitor C1 begins to chargethrough resistor R5. When the potential on the PUT Q2 annode is slightlygreater than the potential of the gate, Q2 will turn on, causing itsgate to pull to ground. This turns off transistor Q3, which turns offQ4, Q5, Q6, and Q7, disconnecting the load resistor and indicators K1and K2. The circuit will remain in this disconnected state until theinput voltage decreases to below the transistor Q1 threshold. Thus,nothing in the circuit turns on until the minimum detect transistor Q1turns on.

Diodes CR1 and CR2 are used with O1 and R3, as are diodes CR4 and CR5with transistor Q4 and resistor R1 1 to provide circuit limiting throughboth these transistors Q1 and Q4. Diode CR3 provides a lower impedencedischarge path for capacitor C1 and diodes CR6 and CR7 are used to shuntback-emf when the K1 and K2 field collapse, these particular indicatorsbeing magnetically operated in the preferred embodiment, although theinvention is not limited in its broadest since to the use of anyparticular indicator type.

Since most of the circuitry draws current simultaneously with the loadresistor, the load resistor is adjusted such that the parallelcombination of the load resistor and other circuits approximates 1.5ohms in the preferred embodiment. The collector-emitter voltage dropacross the transistor Q5 compensates for the other circuitry, thus theload resistor R13 has a valve of approximately 1.5 ohms. When thecurrent through the circuit is 3 amperes, the voltage measured acrossthe circuit is approximately 4.5 volts, indicating that the equivalentload is approximately 1.5 ohms in the preferred embodiment to beexplained in detail subsequently.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary, perspectiveview showing test probe apparatus embodying the principles of theinvention.

FIG. 2 is a circuit diagram of the circuit means including a minimumevent indicator to sense a selected minimum quantity of electricalenergy, and a threshold indicator for sensing a selected quantity ofelectrical energy above said minimum.

FIG. 3 is a fragmentary, side elevation view, in longitudinal sectionshowing the electrical contacts and retainer means that form a portionof the test probe apparatus shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The letter A in FIG. 1designates the housing of a test probe, having on one end retainer meansB for securing the housing to a relief grove, thread grooves or otherindentations in a cartridge well or breech cap of a weapons system.Indicator means C appears on the op posite end of the housing andincludes, as will be subsequently explained, a minimum event indicatorand a threshold indicator, as well ,as circuit means D connected withelectrical contacts (not shown in FIG. 1) generally circumscribed by theretainer means B.

With reference to FIG. 3, the retainer means B consists of a pluralityof latch elements 11, portions thereof adapted to extend outward beyondthe periphery of an annular shell 13 through apertures 15 adjacent aforward wall 17. A ring portion 19 is carried by a movable shell 21mounted on a body 23 for reciprocal movement thereon, the ring portionhaving a plurality of circumferentially spaced apertures 25 adjacent andbehind forward lips 27. When the lips 27 are urged forward, they engagethe extreme end of each associated latch element to force it outwardthrough the aperture 15, the opposite end of the latch element fallingpartially within the aperture 25 of the ring portion 19.

' Upon retraction of the movable shell 21 and ring 19,

the lips 27 of the ring move rearward to the position shown in FIG. 3such that the latch elements 11, due to their arcuate configurationshown, are retracted from the aperture 15. Hence, the latch elements maybe made to engage or disengage thread grooves, relief grooves, orindentations formed inside a cartridge well or breech cap, as isexplained in greater detail in a co pending application entitled LatchType Pyrotechnic Detonator Circuit Test Probe, Ser. No. 777,674, filedNov. 2l, 1968.

Two electrical conductors 29, 31 connect respectively with inner means31 and outer contact means 3.2 that lead to a resiliently mounted innerelectrical contact 37 and a resiliently mounted outer contact 35. Theouter contact 35 consists of an exterior plate engaged by a plurality oftelescopic bellows 39, the larger and outer of which 41 is secured to anannular plate 43. A conical spring 45 connects between the smaller ofsaid bellows 47 and the axially extending sleeve that forms apart ofcontact means 32. The outer contact 35,

bellows 39, conical spring 45, plate 43 and sleeve 49 are allelectrically conducted such that electricity flows therethrough from thecontact 35 to the conductor 31.

The inner contact means 33 includes an axially extending sleeve 33 andreciprocably mounted button 51 having an interior flange 53 retained bythe lip 55 on the sleeve, with a compression spring 57 being mountedbetween the flange 53 and an opposing shoulder 59 on a mandrel 61. Thus,both the inner and outer contact means have linear movement for positiveengagement with the contacts inside the cartridge well or breech cap ofthe weapons release apparatus.

As also shown in FIG. 1, an interior section 63 of the test probehousing consists of a sleeve and preferably utilizes an O ring 65 forengagement with a cap 67 that houses a minimum event indicator K2 and athreshold indicator Kl. Thus, the contact end and indicator ends of thehousing are retained to the sleeve 63 preferably by threaded connectionsas shown in FIG. 1.

The circuit means B located within the sleeve 63 of the test probe isillustrated schematically in FIG. 2, where the outer and inner contactsare represented by the numerals 35 and 37 for connection respectivelywith the conductors 31 and 29, the contacts being referred to sometimesas input terminals in the following circuit description.

A preferably five amp fuse (F 1) 71 is connected in the conductor 31 forcurrent protection against excessively high current. The diode (CR8) 73prevents reversing polarity from damaging the circuit, although inpractice this should not occur since the cartridge well or breech capapparatus in the weapons system provides the correct and positivepolarization. Biasing resistors (R1) 75 and (R2) 77 are seriallyconnected with conductor 31 and the common or ground 29.

A transistor (Q1) 79 has its base connected with the juncture ofresistors (R1) 75 and (R2) 77. The two diodes (CRl) 81 and (CR2) 83 arealso connected with the base of the transistor (Q1) 79, while theresistor (R3) 87 is connected with the emitter of transistor (Q1) 79 toprovide a constant current capability by limiting the current flowthrough the transistor (Q1) 79. Expressed otherwise, the transistor (Q1)79 in combination with the resistor (R3) 87 and the two diodes (CR1) 81and (CR2) 83 provide a constant current means or section to give aconstant voltage output at the juncture 91 of the collector of thetransistor (Q1) 79 and resistor (R4) 93. This allows a predictable timebuild-up for the programmable unijunction transistor (PUT) 95 (Q2) withits emitter and collector connected in the circuit at terminals 97, 99such that the voltage at terminal 97 is preferably 0.6 volts higher thanat terminal 99 for the purpose of turning on transistor (Q2) 95.

A capacitor (C1) 101 and resistance (R5) 103 of a RC network areconnected with the juncture 91 between the collector of the transistor(Q1) 79 and resistance (R4) 93 such that the capacitor (C1) 101 startscharging through the resistor (R5) 103. The transistor (Q2) 95 isconnected through terminal 99 with the juncture of resistor (R5) 103 andthe capacitor (C1) 101 and with the ground or conductor 29. A diode(CR3) 105 is connected with terminal 99 and the juncture 91 to provide adischarge path so capacitor (C1) 101 can discharge rapidly when thetransistor (Q1) 79 turns off. PUT transistor (Q2) 95 is also connectedwith terminal 97 at the juncture of the biasing transistors (R6) 107 and(R7) 109, terminal 97 also being connected with transistor (Q2) 95 asshown.

The base of a transistor (Q3) 11] is connected at the juncture of theresistor (R7) 109 and a resistor (R8) 113 in series therewith that isalso connected with the ground or conductor 29. Accordingly, when thetransistor (Q3) 95 turns on, the transistor (Q3) 111 is renderedconductive. The collector of transistor (Q3) 111 biasing resistors (R9)115 and (R) 117, are serially connected with the conductor 31 andconductor 29. The resistor (R9) 115 insures that the transistor (Q4) 119is turned off when transistor (O3) 111 turns off.

The collector of transistor (Q3) 111 is connected through conductor 121with the base of a transistor (07) 123 by way of a biasing resistor(R18) 125. Another resistor (R17) 127 is serially connected with thebase of transistor (O7) 123 and with the conductor 31. The resistors(R17) 127 and (R18) 125 are biasing resistors to protect the transistor(O7) 123 by limiting the base current flowing through it. When thetransistor (Q3) 111 is rendered conductive, the conductor 121 and hencethe base of the transistor (O7) 123 is brought to ground to turn on itstransistor and trip minimum event indicator (K2) 129. The diode (CR7)131 connected across the indicator (K2) 129 and between the collector ofthe transistor (Q7) 123 and the conductor 29 provide polarityprotection. When the transistor (O3) 111 is rendered conductive, thetransistor (Q4) 135 is rendered conductive, since its base is connectedwith the juncture of resistors (R9) 137 and (R10) 139 that are seriallyconnected with conductor 31 and the juncture of the collector of thetransistor (O3) 111 and conductor 121. Similarly, as with the transistor(Q1) 79, the transistor (Q4) 135 also has diodes (CR4) 141 and (CR5) 143connected with its base and with conductor 31. A resistor (R11) 145 isconnected with the emitter of the transistor (Q4) 135 to provideconstant current safety to limit the current available to the base of atransistor (Q5 147. When the transistor (Q4) 135 is rendered conductive,transistor (Q5) 147 is rendered conductive, since the base of transistor(O5) 147 is connected with the juncture of the collector of transistor(O4) 135 and biasing resistor (R12) 149 that is connected with the baseof transistor (O5) 147 and the ground or conductor 29 to insure that thetransistor (Q5) 147 is turned off when the transistor (Q4) 135 is turnedoff.

The transistor (O5) 147 impresses the basic load (R13) 151 of 1.5 ohmsinto the circuit. The transistor (O5) 147 compensates for the effect ofother elements in the circuit which tend to make the basic load varyfrom 1.5 ohms. Expressed otherwise, the basic load (R13) 151 and thetransistor (Q5) 147 are serially connected with the conductor 31 and theground 29. The biasing resistor (R14) 153, the potential (R15) 155, oneform of variable resistance means, and the biasing resistor (R16) 157are serially connected with conductor 31 and the juncture of thecollector of transistor (Q5) 147 and the resistor (R13) 1511. The outputterminal 159 of the potentiometer (R15) is connected with the base of atransistor (Q6) 161 that has its emitter connected with conductor 31 andits connector connected with the indicator (K1) 163, which has a diode(CR6) connected thereacross as shown to provide polarity protection.

The potentiometer (R15) 155 is set by adjusting the circuit pulses 10milliseconds wide and applying a current of 3 amps and a voltage of 4.5volts across the 1.5 ohm resistance (R13) 151, thereafter adjusting thepotentiometer until the indicator (K1) 163 will initially actuate.

When the transistor (Q5) 147 is rendered conductive, the transistor (Q6)161 is also rendered conductive to begin to actuate the indicator (K1)163.

When the transistor (O5) 147 is rendered conductive, the transistor (Q6)161 is rendered conductive to begin to actuate the energy operatedindicator (K1) 163. If suitable current is applied for a suitableinterval of time, the indicator (Kl) 163 will be actuated to indicatesuitable power to fire pyrotechnic cartridges to be subsequently in thecartridge well or breech cap.

Operationally, the circuit is designed such that it takes 10milliseconds for the transistor (Q2) 95 to turn on after the contacts35, 57 are energized by the firing system of aircraft. When thetransistor (Q2) 95 turns on, the voltage at terminal 97 is dropped toground and the transistor (Q3) 111 is turned off. The transistors (Q4)119 and (O7) 123 are similarly turned off, as is the transistor (O5)143. In the event there is not sufficient power for suitable period oftime to energize the 3 ampere indicator (K1) 163, but there is a minimumof 1 ampere'of current, the indicator (K2) 129 will be actuated. Thetransistor (Q1) 79 remains conductive and the transistor (Q2) 95 latcheson so long as the input terminals are connected with the leadingterminals inside a cartridge well or breech cap. The indicators (Kl) 163and (K2) 129 are retained in their respective positions until reset. Nochanges are experienced in the circuit thereafter until the inputterminals 35, 37 are disconnected from the power source.

The indicators (K1) 163 and (K2) 129 are preferably of the magneticlatching type such as those sold under the trademark Minelco, asubsidiary of General Time of Holbrook, Massachusetts, as shown in theirBulletin B-llA entitled Miniature Bite Indicator, Model BI-lG2lT, havinga rating of 3 volts and 13.8 ohms. However, any indicator means iswithin the broad range of the invention, including indicator usingliquid crystal technology as explained in the July 6, 1970 issue ofElectronics, the McGraw Hill Publication, page 64.

While the invention has been shown in only one of its forms, it shouldbe apparent to those skilled in the art that it is not so limited but issusceptible to various changes and modifications without departing fromthe spirit thereof. For example the invention in its broadest aspects isnot limited to the specific structures shown with the other saidcontacts, and the base of the and the various element values are givenonly by way transistor connected with resistance means conof sample.nected between the first of said contacts and the We claim: collector ofsaid constant current transistor. 1. A current potential indicatorespecially suitable 6. The current potential indicator of claim 5 inwhich fOr WBaPOIIS test y m Said lndiCfltOf mprising: the resistancemeans connected with the base of said a test probe housing, a pair ofelectrical contacts carried by one end region of the housing, latchelements carried by said housing to secure the 10 housing inside aselected test well,

quantity of energy that actuates said threshold indicator.

7. The current potential indicator of claim 1 wherein said loaddisconnect means comprises:

threshold transistor is variable for selectivity of the means connectedwith said latch elements for selective actuation thereof, an electricalbi-stable type minimum event indicator control means for disconnectingsaid circuit means,

capacitor means and resistor means for applying an carriedby i h g, I5electrical input to said control means, an electrical bi-stable typethreshold indicator car- Said Capacitor means b i d t d to b i chargingf y said houslng, after electrical energy from said contacts is appliedcll'ctllt f t Connect?! between 331d PQ and thereto to cause saidcontrol means to electrically 581d mmlmum event mdlcator for Provldmg aflow disconnect said circuit means at a time following path ofelectrical energy from said contacts to said the application felectrical energy to id capaciminimum event indicator when theelectrical energy is at a predetermined minimum level to allow saidminimum event indicator to be actuated solely from the electrical energyderived from the system tor means depending upon the R-C time constantof said capacitor means and said resistor means. 8. An electricalpotential indicator especially suitable for weapons test systemscomprising:

i b a test probe housing, said circuit means also being connectedbetween said input means Carried by Said housing and adapted to contactsand said threshold indicator for providing be ccupled electrically to aSystem to be tested i gzfifilgfi g 133%: 98 $235; g g an electricalbi-stable indicator carried by said housergy is at a predetermined upperthreshold level to a s z g xg g ii gi $55 5 blstable States allow saidthreshold indicator to be actuated solely circuit means iz; between a inM means from the electrical energy derived from the system f fl to betested and and said in icator or pr ovldmg a ow pat of elecloaddisconnect means for automatically disconnectmeal energy from f Inputmeans.to.sald mdlca' ing the circuit means after a selected timeinterval when the eleqmca energy at Sald W of electrical energyapplication 15 at a predetermined level to allow said indicator 2. Thecurrent potential indicator of claim 1 which be actuated solely from theelectrical energy further comprises. rived from the system to be tested,and

a constant current Scurce means Connected with d load disconnect meansfor disconnecting the circuit contacts Said threshold indicator and Saidmini 40 means after a selected time interval of electrical mum eventindicator for supply constant current in emrgy aPphcauon the Circuit.said load disconnect means comprising: 3. The current potentialindicator of claim 2 in which Control maans for dlsconnectmg circuitmeans: said constant current source means comprises:

a constant current transistor having its emitter and capaclto'r mefansand 1 means for PP l an collector connected across said contacts;elecmca l to q 00mm] means, a resistor connected between'said emitterand one of i capacitor mefms bemg adapted P gsaid contacts; mg afterelectrical energy from said input means resistor means connected acrosssaid contacts and 15 PPl thefeto t0 Control means IO with the base fSaid transistor. electrically disconnect said circuit means at a 4. Thecurrent potential indicator of claim 3 in which time follqwmgappllcatlon of electrical said circuit means connecting said contactsand said f Said Capaclmr mefms p g p the minimum event indicatorcomprises: R-C time constant of Sald capacitor means and a minimum eventtransistor having its emitter con- 531d resistor meansnected with one ofsaid contacts, its collector connected with said minimum eventindicator, which is connected with the other of said contacts, and thebase of the transistor connected with resistance means connected betweenthe front of said 9 A current potential indicator especially suitablefor weapons test systems, said indicator comprising:

a test probe housing, a pair of electrical contacts carried by one endregion of the housing,

contacts and the collector of said constant current atch elementsCarried by said housing to secure the transistor, housing inside aselected test well, 5. The current potential indicator of claim I insaid means Connected with said latch element for seleccircuit meansconnected between said contacts and tive actuation thereof, saidthreshold indicator comprises: an electrical bi-stable type minimumevent indicator a threshold transistor having its emitter connected withone of said contacts, its collector connected with said thresholdindicator, which is connected carried by said housing, an electricalbi-stable type threshold indicator carried by said housing,

9 means coupled between said contacts and said minimum event indicatorfor providing a flow path of electrical energy from said contacts tosaid minimum event indicator when the electrical energy is at apredetermined minimum level to allow said minimum event indicator to beactuated solely from the electrical energy derived from the system to betested,

means coupled between said contacts and said threshold indicator forproviding a flow path of electrical energy from said contacts to saidthreshold indicator when the electrical energy is at a predeterminedupper threshold level to allow said threshold indicator to be actuatedsolely from the electrical energy derived from the system to be tested,

transistor means coupled to each of said indicators for controlling theflow of electrical energy to said indicators,

a generally constant current source means including an input transistorcoupled to said contacts which becomes conductive when the input theretois above a given level,

a control transistor coupled to the output of said input transistor andto said transistor means for allowing the flow of electrical energy tosaid transistor means when said control transistor is renderedconductive by the output of said input transistor,

an R-C circuit including capacitor and resistor means coupled to theoutput of said input transistor, and

means coupled to said R-C circuit for rendering said control transistornonconductive after a predetermined time interval after said inputtransistor becomes conductive dependent upon the R-C time constant ofsaid capacitor means and said resistor means.

able for weapons test systems comprising:

a test probe housing,

input means carried by said housing and adapted to be coupledelectrically to a system to be tested,

an electrical bi-stable indicator carried by said housing and whichremains in one of its bi-stable states when electrical energy isremoved,

means coupled between said input means and said indicator for providinga flow path of electrical energy from said input means to said indicatorwhen the electrical energy at said input means is at a predeterminedlevel to allow said indicator to be actuated solely from the electricalenergy derived from the system to be tested,

transistor means coupled to said indicator for controlling the flow ofelectrical energy to said indicator,

a generally constant current source means including an input transistorcoupled to said input means which becomes conductive when the inputthereto is above a given level,

a control transistor coupled to the output of said input transistor andto said transistor means for allowing the flow of electrical energy tosaid transistor means when said control transistor is renderedconductive by the output of said input transistor,

an R-C circuit including capacitor and resistor means coupled to theoutput of said input transistor, and

means coupled to said R-C circuit for rendering said control transistornonconductive after a predetermined time interval after said inputtransistor becomes conductive dependent upon the R-C time constant ofsaid capacitor means and said resistor

1. A current potential indicator especially suitable for weapons testsystems, said indicator comprising: a test probe housing, a pair ofelectrical contacts carried by one end region of the housing, latchelements carried by said housing to secure the housing inside a selectedtest well, means connected with said latch elements for selectiveactuation thereof, an electrical bi-stable type minimum event indicatorcarried by said housing, an electrical bi-stable type thresholdindicator carried by said housing, circuit means connected between saidcontacts and said minimum event indicator for providing a flow path ofelectrical energy from said contacts to said minimum event indicatorwhen the electrical energy is at a predetermined minimum level to allowsaid minimum event indicator to be actuated solely from the electricalenergy derived from the system to be tested, said circuit means alsobeing connected between said contacts and said threshold indicator forproviding a flow path of electrical energy from said contacts to saidthreshold indicator when the electrical energy is at a predeterminedupper threshold level to allow said threshold indicator to be actuatedsolely from the electrical energy derived from the system to be tested,and load disconnect means for automatically disconnecting the circuitmeans after a selected time interval of electrical energy application.2. ThE current potential indicator of claim 1 which further comprises: aconstant current source means connected with said contacts, saidthreshold indicator, and said minimum event indicator for supplyconstant current in the circuit.
 3. The current potential indicator ofclaim 2 in which said constant current source means comprises: aconstant current transistor having its emitter and collector connectedacross said contacts; a resistor connected between said emitter and oneof said contacts; resistor means connected across said contacts and withthe base of said transistor.
 4. The current potential indicator of claim3 in which said circuit means connecting said contacts and said minimumevent indicator comprises: a minimum event transistor having its emitterconnected with one of said contacts, its collector connected with saidminimum event indicator, which is connected with the other of saidcontacts, and the base of the transistor connected with resistance meansconnected between the front of said contacts and the collector of saidconstant current transistor.
 5. The current potential indicator of claim1 in said circuit means connected between said contacts and saidthreshold indicator comprises: a threshold transistor having its emitterconnected with one of said contacts, its collector connected with saidthreshold indicator, which is connected with the other said contacts,and the base of the transistor connected with resistance means connectedbetween the first of said contacts and the collector of said constantcurrent transistor.
 6. The current potential indicator of claim 5 inwhich the resistance means connected with the base of said thresholdtransistor is variable for selectivity of the quantity of energy thatactuates said threshold indicator.
 7. The current potential indicator ofclaim 1 wherein said load disconnect means comprises: control means fordisconnecting said circuit means, capacitor means and resistor means forapplying an electrical input to said control means, said capacitor meansbeing adapted to begin charging after electrical energy from saidcontacts is applied thereto to cause said control means to electricallydisconnect said circuit means at a time following the application ofelectrical energy to said capacitor means depending upon the R-C timeconstant of said capacitor means and said resistor means.
 8. Anelectrical potential indicator especially suitable for weapons testsystems comprising: a test probe housing, input means carried by saidhousing and adapted to be coupled electrically to a system to be tested,an electrical bi-stable indicator carried by said housing and whichremains in one of its bi-stable states when electrical energy isremoved, circuit means connected between said input means and saidindicator for providing a flow path of electrical energy from said inputmeans to said indicator when the electrical energy at said input meansis at a predetermined level to allow said indicator to be actuatedsolely from the electrical energy derived from the system to be tested,and load disconnect means for disconnecting the circuit means after aselected time interval of electrical energy application, said loaddisconnect means comprising: control means for disconnecting saidcircuit means, capacitor means and resistor means for applying anelectrical input to said control means, said capacitor means beingadapted to begin charging after electrical energy from said input meansis applied thereto to cause said control means to electricallydisconnect said circuit means at a time following the application ofelectrical energy to said capacitor means depending upon the R-C timeconstant of said capacitor means and said resistor means. 9 A currentpotential indicator especially suitable for weapons test systems, saidindicator comprising: a test probe housing, a pair of electricalcontacts carried by one end rEgion of the housing, latch elementscarried by said housing to secure the housing inside a selected testwell, means connected with said latch element for selective actuationthereof, an electrical bi-stable type minimum event indicator carried bysaid housing, an electrical bi-stable type threshold indicator carriedby said housing, means coupled between said contacts and said minimumevent indicator for providing a flow path of electrical energy from saidcontacts to said minimum event indicator when the electrical energy isat a predetermined minimum level to allow said minimum event indicatorto be actuated solely from the electrical energy derived from the systemto be tested, means coupled between said contacts and said thresholdindicator for providing a flow path of electrical energy from saidcontacts to said threshold indicator when the electrical energy is at apredetermined upper threshold level to allow said threshold indicator tobe actuated solely from the electrical energy derived from the system tobe tested, transistor means coupled to each of said indicators forcontrolling the flow of electrical energy to said indicators, agenerally constant current source means including an input transistorcoupled to said contacts which becomes conductive when the input theretois above a given level, a control transistor coupled to the output ofsaid input transistor and to said transistor means for allowing the flowof electrical energy to said transistor means when said controltransistor is rendered conductive by the output of said inputtransistor, an R-C circuit including capacitor and resistor meanscoupled to the output of said input transistor, and means coupled tosaid R-C circuit for rendering said control transistor nonconductiveafter a predetermined time interval after said input transistor becomesconductive dependent upon the R-C time constant of said capacitor meansand said resistor means.
 10. An electrical potential indicatorespecially suitable for weapons test systems comprising: a test probehousing, input means carried by said housing and adapted to be coupledelectrically to a system to be tested, an electrical bi-stable indicatorcarried by said housing and which remains in one of its bi-stable stateswhen electrical energy is removed, means coupled between said inputmeans and said indicator for providing a flow path of electrical energyfrom said input means to said indicator when the electrical energy atsaid input means is at a predetermined level to allow said indicator tobe actuated solely from the electrical energy derived from the system tobe tested, transistor means coupled to said indicator for controllingthe flow of electrical energy to said indicator, a generally constantcurrent source means including an input transistor coupled to said inputmeans which becomes conductive when the input thereto is above a givenlevel, a control transistor coupled to the output of said inputtransistor and to said transistor means for allowing the flow ofelectrical energy to said transistor means when said control transistoris rendered conductive by the output of said input transistor, an R-Ccircuit including capacitor and resistor means coupled to the output ofsaid input transistor, and means coupled to said R-C circuit forrendering said control transistor nonconductive after a predeterminedtime interval after said input transistor becomes conductive dependentupon the R-C time constant of said capacitor means and said resistormeans.